[FieldTrip] Power Time Course

Roemer van der Meij r.vandermeij at donders.ru.nl
Tue Nov 8 23:19:35 CET 2011

Hi Francesco,

I don't entirely understand what you referring to either, but it sounds 
at least like a within channel phenomenon? In that case, you can use 
cfg.output = 'pow', or 'fourier', which do not compute the between 
channel CSD, saving quite a bit memory.

If you are interested in the total energy over time of your signal, but 
only for the 1-150 Hz part, it might be easier to do a bandpass, and 
taking the square of your raw signal (energy is usually squared 
amplitude I thought?). If that is what your intending though.


On 08/11/2011 11:33, Eelke Spaak wrote:
> Dear Francesco,
> Your question is not entirely clear to me. Do you want to estimate the
> timecourse of the total (i.e. non-frequency-resolved) power in your
> signal? In that case, frequency analysis is not the way to go;
> basically your signal itself contains this information already (you
> may want to rectify (abs()) it first, or apply a hilbert transform).
> Also, I don't understand the reference to ft_componentanalysis.
> Furthermore, the code you paste in your email seems valid to me. (You
> could possibly simplify it by using cfg.toi = comp.time{1}; to get an
> estimate of power at each time point in your signal. ) What does not
> seem to work, in your case?
> Best,
> Eelke
> 2011/11/8<f.dipompeo at unich.it>:
>> I would like to know if there is a ft function to calculate the Time Course
>> of Power of Electric and Magnetic Channels and IC coming from
>> ft_componentanalysis in the case of continuous resting state data.
>> I tried to do it using ft_freqanalysis with 'mtmconvol' as method and a
>> "toi" large as my whole acquisition time window (the script is below).
>> Time Course of Power should be obtained by summing up the results over all
>> the frequencies.
>> Thank you very much,
>> Francesco
>> -------------------------------------------------------
>> cfg=[];
>> cfg.method = 'mtmconvol';
>> cfg.output = 'powandcsd';
>> cfg.taper = 'hanning';
>> cfg.trials = 'all';
>> cfg.foi = 1:150;
>> cfg.toi = [comp.time{1}(1,1):0.02:comp.time{1}(1,end)];
>> cfg.t_ftimwin = 4./cfg.foi;
>> [freq_comp_tr] = ft_freqanalysis(cfg,comp);
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Roemer van der Meij M.Sc.
PhD student
Donders Institute for Brain, Cognition and Behaviour
Centre for Cognition
P.O. Box 9104
6500 HE Nijmegen
The Netherlands
Tel: +31(0)24 3655932
E-mail: r.vandermeij at donders.ru.nl
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